The invention relates to a liquid crystal display device for use as a display panel in various electronic equipment such as a timepiece (watch and clock), portable information equipment, and so forth.
A timepiece for indicating digital display of time information such as the hour, minute, and second, and calendar information such as the date, days of the week, the month, and the year, by use of a liquid crystal display panel, has been in widespread use for wrist watches and clocks, provided with a crystal oscillation circuit
There has also been in use a combination watch wherein an analog display indicating time information by the hands of the watch is used in combination with digital display indicating time information and calendar information in numbers and letters.
Further, there has been proposed an analog watch for selectively displaying markers in various patterns, or for displaying simulated hands for an hour hand, a minute hand, and a second hand, by providing the dial thereof based on a liquid crystal display panel (refer to, for example, Japanese Patent Laid-open S54-153066).
A reflective-type liquid crystal display device, small in size and consuming very little electric power, has been in widespread use as a display panel for displaying necessary information (character information and graphic information) in various electronic equipment other than a timepiece, such as cellular phones, desktop electronic computers, game players, and so forth.
As such a liquid crystal display device as described above, in a conventional liquid crystal display panel, a liquid crystal cell filled with liquid crystals is sandwiched between two transparent substrates having an electrode on respective inner surfaces thereof, facing each other, and an upper polarizing film and a lower polarizing film are disposed, respectively, on the external surface of the transparent substrates, on the opposite sides. If an electric field is applied to the liquid crystals by applying a voltage to a pair of electrodes on the transparent substrates holding the liquid crystal cell therebetween, the optical property of the liquid crystals is changed, thereby locally controlling transmission and absorption of light falling on the liquid crystal display panel such that a predetermined display is effected.
Either of the upper polarizing film or the lower polarizing film is a polarizing film absorbing the light linearly polarized in the direction orthogonal to the transmission axis thereof.
In the case of a watch using the conventional liquid crystal display panel described above, time information and calendar information are displayed in black against a white background in a normally white mode that is common.
However, by simply displaying time information and calendar information in black against the white background as described in the foregoing, neither variation in design nor interest can be offered, with a resulting tendency to lose soon popularity with consumers. Probably, as a result, consumption of digital watches has recently been on the decline, and neither combination watches nor analog watches with a liquid crystal display panel have since received market acceptance.
Similarly, with the conventional liquid crystal display panel used in electronic equipment other than a timepiece, various information expressed in characters and graphics is generally displayed in black against the white background, and although there are some wherein information can be displayed in white against the black background in an inverse mode, the conventional liquid crystal display panel has still been found lacking in design variation and aesthetic qualities.
In light of the present situation as described, the present invention has been developed, and an object of the invention is to provide a liquid crystal display device for use in various electronic equipment such as a timepiece (watch and clock), and so forth, capable of offering attractive variation in design and displaying information clearly so that a viewer can see the display with greater ease.
To this end, the invention provides a liquid crystal display device comprising a first liquid crystal cell and disposed on the visible side made up of a liquid crystal layer sealed in a gap between a pair of transparent substrates having an electrode formed on each of the inner surfaces thereof, facing each other; a second liquid crystal cell disposed on the backside of the first liquid crystal cell; an absorption-type polarizing film disposed on the visible side of the first liquid crystal cell, for absorbing the light linearly polarized in the direction orthogonal to the transmission axis thereof; and a reflection-type polarizing film disposed on a side of the second liquid crystal cell opposite from the visible side thereof, for reflecting the light linearly polarized in the direction orthogonal to the transmission axis thereof.
Further, a reflector or a color filter may be disposed on a side of the reflection-type polarizing film, opposite from the visible side thereof.
In the case of the color filter being disposed, any of a selective-transmission-type color filter, a selective-transmission-type color polarizing film, and a dielectric multi-layered filter may be used.
A light scattering film may be disposed on the visible side of the absorption-type polarizing film.
A light scattering film may be disposed on the visible side of the absorption-type polarizing film while a reflector or a color filter may be disposed on a side of the reflection-type polarizing film, opposite from the visible side thereof.
A color filter may be disposed on a side of the reflection-type polarizing film, opposite from the visible side thereof while a reflector may be disposed on a side of the color filter, opposite from the visible side thereof. Further, a light scattering film may be disposed on the visible side of the absorption-type polarizing film.
Alternatively a backlight may be disposed on a side of the reflection-type polarizing film, opposite from the visible side thereof. In such a case, any of an electroluminescence light, a light-emitting diode array, a hot cathode fluorescent lump, and a cold-cathode fluorescent lamp may be adopted for the backlight.
In this case, a transflective reflector or a color filter is preferably disposed between the reflection-type polarizing film and the backlight
Even in this case, a light scattering film is preferably disposed on the visible side of the absorption-type polarizing film.
A color filter and a transflective reflector may be disposed between the reflection-type polarizing film and the backlight
With any of the liquid crystal display devices described above, it is desirable that the absorption-type polarizing film and the reflection-type polarizing film are disposed such that respective transmission axes are orthogonal to or parallel with each other.
A liquid crystal layer of the first liquid crystal cell and the second liquid crystal cell, respectively, is preferably composed of liquid crystals causing linearly polarized light passing therethrough to undergo phase modulation or intensity modulation.
The liquid crystal layers of the first liquid crystal cell and the second liquid crystal cell, respectively, are preferably composed of any of twisted nematic liquid crystals, supertwisted nematic liquid crystals and guest-host liquid crystals.
In the case of the guest-host liquid crystals, use of guest-host liquid crystals having homogeneous alignment or homeotropic alignment, in an initial alignment thereof, is preferable.
Alternatively the liquid crystal layers of the first liquid crystal cell and the second liquid crystal cell, respectively, may be composed of ferroelectric liquid crystals or anti-ferroelectric liquid crystals.
In the case where the liquid crystal layer of the first liquid crystal cell is composed of twisted nematic liquid crystals, or guest-host liquid crystals having homogeneous alignment or homeotropic alignment, in an initial alignment thereof, the transmission axis of the absorption-type polarizing film is preferably oriented in a direction orthogonal to or parallel with the long axes of liquid crystal molecules in the liquid crystal layer of the first liquid crystal cell, on the visible side thereof.
In the case where the liquid crystal layers of the first liquid crystal cell and the second liquid crystal cell, respectively, are composed of twisted nematic liquid crystals, it is desirable that the transmission axis of the absorption-type polarizing film is oriented in a direction orthogonal to or parallel with the long axes of liquid crystal molecules in the liquid crystal layer of the first liquid crystal cell, on the visible side thereof, the long axes of liquid crystal molecules in the liquid crystal layer of the first liquid crystal cell, on a side thereof, opposite from the visible side, are oriented in a direction parallel with or orthogonal to the long axes of liquid crystal molecules in the liquid crystal layer of the second liquid crystal cell, on the visible side thereof, and the long axes of liquid crystal molecules in the liquid crystal layer of the second liquid crystal cell, on a side thereof, opposite from the visible side, are oriented in a direction parallel with or orthogonal to the transmission axis of the reflection-type polarizing film.
If whole-surface electrodes are adopted for both the electrodes formed on the inner surfaces of the pair of the transparent substrates of the first liquid crystal cell, facing each other, the function of an optical shutter for display in a metallic tone can be provided.
With the liquid crystal display device according to the invention, having the construction described above, information expressed in characters, graphics, and so forth can be displayed in a transparent state, in a black color, or in an optional color against a background in a metallic tone, or conversely, display of the information such as characters, graphics, and so forth, in a metallic tone, can be effected in a high contrast against the background displayed in a transparent state, in a black color, or in an optional color. Further, transmission-type display can also be effected at night, and so forth by installing a backlight.